"Finding ways to support use of daily pill is focus of [the] next studies," said Grant, adding that future studies should determine whether more limited and shorter term use of the pill, along with other available prevention methods, may prove just as effective.
"Sustainability of treatment programs requires that something needs to be done to decrease infection [rates]," Grant said.
Truvada is commonly used as a therapy for patients already infected with HIV. In most countries, the pill costs about 40 cents a day, Grant said. However, Grant added that it's likely the price of the drug will rise if used as a prevention method. The study may prompt use of the drug in more countries.
In fact, in Peru, which is one of the countries that partook in the study, the drug is currently not available to the nearly 42,000 people infected with HIV. Fifty-five percent of study participants came from Peru, according to study co-chair Lama.
Still, researchers said it is too early to tell when the drug will be used. Researchers said it's also unlikely public health HIV prevention plans will incorporate wide use of the PrEP pill soon because there are too many questions still unanswered.
"What about women? What about heterosexual activities? What about the long term?" said Fauci, who also added that it's unclear whether taking the drug daily for longer than two years could cause complications.
Although the study was limited to one type of high-risk group, other PrEP studies are looking at other groups at risk for transmission, including heterosexual couples and intravenous drug users. Researchers also plan to conduct a longer term follow up study to iPrEx beginning 2011.
"We don't have answers to questions on public health [concerns] to determine whether and how these findings should be incorporated into ongoing HIV programs," Fauci said. "We anticipate that other PrEP studies being conducted will provide a more comprehensive view."